Not a complete list but:
Use "A" or "P" modes
Try to keep ISO at 100. 200 is OK but you can still get some noise in shadows.
Noise reduction to -1 for enhanced sharpness
EV at -.33 or -.67
Use "blinkies" to avoid clipped highlights
Shoot RAW + JPEG if you want to post-process
Get used to the focus lever on the lens barrel for macro.
I too went from the FZ28 to the FZ150. It's a wonderful camera and for me, there is no need or even desire to upgrade to the FZ200. The one thing which will startle you is the excellence of the image stabilisation. You can take hand-held telephoto shots at unbelievably slow shutter speeds (though of course, faster is normally better). You can also take a lot of indoor shots without flash (when the FZ28 would have needed some extra lighting)
All very good advice. I use NR at -1 and sharpness at 0. I tried sharpness at +1 since some recommend that, but I decided the images were a little over sharp.
Regarding the image stabilization, it is good enough to use shutter speeds as low as 1/250 at full zoom, usually. Using the EVF helps hold it steady. Go below this and you might be disappointed. Use S mode in these cases if necessary to keep the shutter speed up. Be aware of the limited depth of field at full zoom; use spot focus.
I'd be very interested in seeing some images. Some claim the Leica has better IQ than the Panny. I'm skeptical. But I have never seen a head-to-head comparison.